[1] Univ Philippines Manila, Dept Epidemiol & Biostat, Coll Publ Hlth, Manila, Philippines
[2] Mahidol Univ, Fac Publ Hlth, Dept Community Hlth, Bangkok, Thailand
[3] SEAMEO TROPMED Network, Bangkok, Thailand
[4] Mahidol Univ, Fac Trop Med, Dept Trop Hyg, 420-6 Ratchawithi Rd, Bangkok 10400, Thailand